1. Field of the Invention
This invention relates to a pneumatic control valve system.
2. Description of the Related Art
A pneumatic control valve system for the control of a hydraulic system, such as a dump truck hoist, is known. For control of a dump truck hoist, one pneumatic valve typically controls the raising of the dump body and a second pneumatic valve controls the lowering of the body. Typically, a lever associated with the valves and may be pivoted in one direction to depress one of the pneumatic valves and in an opposite direction to depress the other pneumatic valve. In controlling a hydraulic system, the pneumatic control valve system must typically provide a further function. For example, with a dump truck hoist, it is necessary to engage the power take-off (referred to as the "PTO") in order to raise the hoist. As is well understood by those skilled in the art, the PTO is a gear in the transmission which must be engaged to run the hydraulic oil pump. In known pneumatic control valve systems, a separate lever or switch is typically employed to engage the PTO. However, the operator must remember to disengage the PTO prior to driving off as, otherwise, the oil pump will be driven at destructive high speeds.
This invention seeks to overcome drawbacks in the known prior art.